it is in the spec... see  bug 635151  and associated folio link. It's the row of blue buttons.

There is no "Call to action" style in the folio link.

https://folio.googleplex.com/chrome-ux-specs-and-sources/Chrome%20browser%20(MD)/Secondary%20UI%20Previews%20and%20specs%20(exports)#%2F_P%20-%20Chrome%20-%20stickersheet.png shows Primary and Secondary style buttons. Are you saying that "Call to action" is a different name for Primary?

That folio link is not the one in the above bug. See SPEC-secondary-UI-01a-buttons-light-theme.png to see why my comment about the row of blue buttons makes sense.

But to answer your question, yes, that sticker sheet uses the term Primary.

I saw your link and it did not answer the question for me. It's not clear why it would.

The viewsexample mini app has a "Material Design" button and (apparently, because it's not visible) a "Call to action" button. I guess those correspond to "Secondary" and "Primary", respectively? The code and the spec should match in terms of names, otherwise it's very confusing figuring out what is what.

> It's not clear why it would.

>> It's the row of blue buttons.

> The code and the spec should match in terms of names

There may be a good reason why Alan chose "Primary", "Secondary", and "Tertiary", but I don't know what it is, and those terms are too generic to make any sense to me. "Call to action" makes sense, and FWIW predates the current sticker sheet.

Regardless of which came first, the situation now is the spec contains one set of names, which differs from the code. This means that when a designer creates a dialog and says that it should include a Primary button, the engineer has to figure out (somehow) that a Primary button in the spec means a "Call to action" button in the code.

I don't think there's anything particularly clear about the name "call to action" - that's advertising terminology that actually confused me, because we're laying out UIs, not constructing ads. Im fact I thought it was some kind of one-off button type for some special case situations. Primary, I assume, refers to the primary action of the dialog. Secondary then refers to the secondary action(s).

Given that the spec defines everything, it seems like the code should match the spec.

"Call to action in web design — and in user experience (UX) in particular — is a term used for elements in a web page that solicit an action from the user."[1] 

You've defined "primary" by using the word "primary". This doesn't elucidate anything. The difference in styles indicates which button we encourage users to press. All dialogs do (or should) have a bias. These buttons say "click me!". Does that help explain the meaning of "call to action"?

[1] https://www.smashingmagazine.com/2009/10/call-to-action-buttons-examples-and-best-practices/

I didn't say I don't understand what "call to action" means - I do, because I've written quite a few ads. I'm saying that your choice of "call to action" for a button name was confusing to me because it's not a UI term. Your link talks about "call to action" buttons because it's about designing ads.

I haven't defined "primary" by using the word "primary." The Primary button's name just also happens to be the same as its function (which is as it should be).